Cathode ray tube



April 24, 1956 K. A. HOAGLAND CATHODE RAY TUBE Filed NOV. 2, 1951 mw om@T A NL) E G www 1H AJM., m .NLV/ MY KB ATTORNEYS A lnited CATHODE RAYTUBE Kenneth A. Hoagland, Nutley, N. J., assignor to Allen B. Du MontLaboratories, Inc., Clifton, N. J., a corporation of Delaware vApplication November 2, 1951, Serial N o. 254,575 9 Claims. (Cl. 31517)The present invention relates to cathode ray tubes and particularly toimprovements in cathode ray tubes of the post deflection accelerationtype.

Cathode ray tubes in which electron acceleration is obtained afterdeflection have the desirable characteristic of a high degree ofdeflection sensitivity at substantially lower deflection controlvoltages. Heretofore, this desirable characteristic has been obtained incathode ray tubes by providing either an electrically conductive ring ora plurality of electrically conductive rings spaced between thedeflection means and the screen of the tube. Such rings' have commonlybeen referred to as intensifier rings and where a single ring has beenutilized, the tube is generally operated with the ring at a voltagesubstantially higher than the anode voltage to obtain the desiredelectron acceleration. Where a series of spaced rings have beenutilized, the tube is generally operated with each of the rings atvoltages substantially higher than the anode voltage and at successivelyincreased voltage as the rings approach the screen.

Tubes of these types have not been entirely satisfactory, however,because of the electron lens effect caused by the rings and theconsequent distortion of the beam along paths angularly displaced fromthe central axis of the tubes.

Accordingly, it is an object of the present invention to provide animproved cathode ray tube of the post deflection acceleration type.

It is another object of the present invention to provide an improvedcathode ray tube of the post deflection acceleration type in which postdeflection beam distortion is substantially eliminated.

lt is still another object of the present invention to provide animproved cathode ray of the post deflection acceleration type in whichthe electron lens effect is substantially eliminated between thedeflection means and the screen of the tube. l

These and other desirable objects are attained in accordance with thepresent invention by providing a cathode ray tube in which accelerationof the electrons is obtained after deflection thereof by an electronacceleration region in the tube formed by spaced electrically conductiveelements positioned transversely of the tube and adjacent the screen.

For a better understanding of the invention, reference may be had to thefollowing description along with the drawing in which Figure l is' alongitudinal crosssectional View with parts broken away of a cathode ray`tube embodying the present invention and Figure 2 is a diagrammaticillustration ofv the tube with a schematic illustration of circuitrelationship of the elements of the tube.

Referring now to the drawing and particularly to Figure 1, there isillustrated a cathode ray tube embodying Vthe present invention andcomprising a substantially tubular container 2 which is generally madeof glass but vmay be made of other suitable materials. One end of thecontainer is reduced to provide a neck portion 4 and the other end ofthe container is provided with a face plate 6. Supported within the neckportion 4 is an electron gun 8 such as are commonly used in cathode raytubes and comprising a cathode 10, a grid 12, a first acceleratingelectrode 14,'a focussing electrode 16 sometimes referred to as a firstanode, and a secondl accelerating electrode y18 also known in the art asa second anode. Each of the aforementioned elements are supported inaxial alignment in a unitary assembly within the neck portion by apairof insulating rods 20.*v A pair of horizontal deflection plates 22 and apair of vertical deflection plates 24 are secured in spaced relationshipon opposite sides of the longitudinal axis of the electron gun and arerespectively positioned parallel with the perpendicular cross-sectionalaxes of the electron gun, and at one end thereof. The deflection platesare secured to supporting wires 26 which, in turn, are supported by apair of insulating discs 27, one of which is attached to the ends of theinsulating rods 20, as shown.

While I have illustrated and described a cathode ray tube structureespecially adapted to utilize electrostatic means' such as deflectionplates for horizontal and Avertical detlection of the electron beam, itwill be obvious that deflection of the beam may be obtained by wellknownmeans other than deflection plates, such as an electromagnetic yokewhich is supported externally of the neck of the tube.

The face 6 of the cathode ray` tube 2 is provided on its inner surfacewith a fluorescent coating 28 and an electrically conductive screen orcoating 30. The coating 30, as shown, s formed on the surface of thefluorescent coating 28 and is accordingly provided with electronpermeable characteristics. In this connection, it should be understoodthat a transparent metallic electrically conductive screen interposedbetween the face of the tube and the fluorescent coating would beequally as effective for the purposes of this invention as screen 30. Anelectrically conductive lead 32 provides an external connectionfor thescreen 30.

Spaced from the screen 30 is a grid assembly 34 comprising spaced grids36 and 38. Grids 36 and 38 are electrically conductive discs supportedtransversely of the tube and are provided respectively with a pluralityof equally spacedsmall apertures 40 and ,42 throughout the entirecross-section thereof. The discs 36 and 38 are positioned in the tubewith the apertures 40 and 42 in alignment along axes parallel to thecentral axis of the tube and discs and apertures 42 are formed with across-sectional diameter substantially larger than that of apertures 40to avoid the interception of electrons which have passed through theapertures ,40 of disc 36. External terminals 44 and 46 passing throughthe tube wall provide means for electrical connections with the discs 36and 38. Likewise prongs 448 in the base 50 provide electricalconnections with the cathode 10, grid 12, focussing electrodel anddeflection plates 22 and 24. An electrical conductive coating 52 on theinner surface of the tube which is-in circuit conducting relationshipwith disc 36 and the spring fingers of a support member 54 connected tothe electrodes 18 and 14 in a manner to be described hereinafter inconnection with Figure 2 of the drawing provides means for connectingthese electrodes with an external source of potential.

For a 4better understanding of the operation of the cathode ray tube ofthe present invention, reference may be had to Figure 2 of the drawing.In this figure, 56 illustrates a -source of accelerating potential forthe electron gun 8. Focussing electrode 16 of the electron gun S isconnectedby lead wire 58 to source 56 at an intermediate potentialterminal of the source while electrodes connecting potential to saidelectrically conductive screen and to one of said grids to provide anelectron accelerating force therebetween.

5. An electron discharge device comprising an envelope having auorescent screen, an electrically conductive surface adjacent saiduorescent screen, an electron gun for generating and directing electronstoward said screen, a Iirst grid positioned between said gun and saidscreen and having electron-permeable openings therein, and a second gridadapted to operate at a potential lower than the potential of said iirstgrid and positioned between said iirst grid and said screen, withelectron-permeable openings therein in alignment with the path of saidelectrons to permit said electrons to pass therethrough and to preventsaid electrons from striking the conductive portions thereof said iirstand said second grids being substantially parallel to said conductivescreen.

6. An electron discharge device comprising an envelope having a targetface, a iluorescent screen on said face, an electrically conductivescreen positioned in said envelope adjacent said uorescent screen, anelectron gun positioned in said envelope for directing a stream ofelectrons toward said uorescent screen, a pair of grids positioned insaid envelope between said electrically conductive screen and said gunand substantially parallel to said conductive screen, a source ofpotential, means connecting said source of potential to said grids tocause the grid nearer said screen to be negative with respect to theother of said pair of grids, and means connecting said source ofpotential to said electrically conductive screen and the grid nearestthereto to cause an electron accelerating force therebetween.

7.An electron discharge device comprising an envelope having a targetface, a uorescent screen on said face, an electrically conductive screenpositioned in said envelope adjacent said uorescent screen, an electrongun positioned in said envelope for directing a stream of electronstoward said fluorescent screen, a pair of grids positioned in saidenvelope between said electrically conductive screen and said gun andsubstantially parallel to said conductive screen, a source of potentialhaving an intermediate terminal and a second terminal less thanapproximately 100 volts negative with respect to said intermediateterminal and a third terminal positive with respect to said intermediateterminal by approximately 20,000 volts, means connecting saidintermediate terminal the grid nearest said gain and connecting saidsecond terminal to the other grid and means connecting said thirdterminal to said electrically conductive `screen to cause saidelectrically conductive screen to be positive with respect to the gridadjacent thereto.

8. An electron discharge device comprising an enve lope having a targetface, a uorescent screen on said face, an electrically conductive screenpositioned in said envelope adjacent said uorescent screen, an electrongun positioned in said envelope for directing a stream of electronstoward said fluorescent screen, a iirst and a second perforated gridplate positioned in order in said envelope between said gun andconductive screen and transversely of the longitudinal axis of saidenvelope and substantially parallel to each other and to said conductivescreen, said plates having their perforations in electron path alignmentwith the electron path to substantially prevent electrons from strikingsaid second grid after passing through the perforations in said firstgrid, a source of potential, means connecting said source of potentialto said tirst and second grids to cause said rst grid to be positivewith respect to said second grid and means connecting said source ofpotential to said electrically conductive screen and to said second gridto cause said electrically conductive screen to be positive with respectto said second grid.

9. The apparatus of claim 8, in which the perforations in said secondgrid plate are larger than the perforations in said lirst grid plate.

References Cited in the tile of this patent UNITED STATES PATENTS Re.23,672 Okolicsanyi June 23, 1953 1,810,018 Howes June 16, 1931 2,029,639Schlesinger Feb. 4, 1936 2,118,865 Schlesinger May 31, 1938 2,165,308Skellett July 11, 1939 2,315,367 Epstein Mar. 30, 1943 2,532,511Okolicsanyi Dec. 5, 1950 2,606,303 Bramley Aug. 5, 1952 2,692,532Lawrence Oct. 26, 1954

